But although we loved her musical note Valentino gown, it was her dramatic hairdo we couldn't keep our eyes off!
The 'Roar' singer swept her jet black locks into a glossy twisted bun which sat high on the top of her head.
The songstress liked her show-stopping updo so much, she even rocked it to the Universal Music Group after-party later that evening, simply swapping her white dress for a floaty blue number.
Fancy recreating a similar look at home? You're in luck!
Lee Radley, Third Senior Director at Nicky Clarke, gave us his top tips for an impressive barnet just like Katy's:
1. Wash and condition your hair, then blow-dry using a paddle brush to create a smooth finish.
2. Sweep your hair back into a mid-ponytail (halfway between the crown of your head and the nape of your neck) and secure with a hairband. To create a large bun like Katy's, Lee suggests using a hair piece for added volume (try this Clip-on Ponytail, £21.99 from Hair Rehab London).
3. Taking a large hair doughnut the same colour as your hair (like this Doughnut Ring, £4.99 from Superdrug), pull onto the base of your ponytail and secure with a hair grip.
4. Now for the slightly tricky part! Take a section from your pony measuring about one inch, twist it and lightly spray with Nicky Clarke Hold and Shine Ultimate Hairspray, £10. Wrap this section around the doughnut, tucking it underneath, and continue wrapping it around until you get to the end of your hair. Pin into place.
5. Keep repeating this step with one-inch sections of hair. Make sure each section follows directly behind the other so that the doughnut is completely covered.
6. Once complete, spritz with a little hairspray to secure and help give a glossy finish.
Alternatively, if you're in a hurry why not fake it? Simply attach a clip-on piece like this Instant Celebrity Bun, £22.99 from Beauty Works, and you're good to go!
What do you think of Katy's hairdo? Let us know by commenting below as the best comment across the site each week wins £50!
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Check out all the red carpet gowns from last night's Grammys:
Copyright: WENN Adriana M. Barraza